Embodiments of the present invention relate to a method of manufacturing an array substrate of transreflective liquid crystal display.
Recently, liquid crystal displays (LCDs) have prevailed in the market of flat panel displays (FPDs). LCDs can be divided as a vertical electric field type and a horizontal electric field type according to the direction of the electric field applied for driving the liquid crystal molecules. A twist nematic (TN) LCD belongs to the vertical electric field type; and a fringe field switching (FFS) LCD and an in-plane switching (IPS) LCD belong to the horizontal electric field type.
In the vertical electric field type LCD, the pixel electrode is formed on an array substrate and the common electrode is formed on a color filter substrate; however, in the horizontal electric field type LCD, both the pixel electrode and the common electrode are formed on the same array substrate. Therefore, an additional process to form the common electrode is required during manufacturing the array substrate of the horizontal electric field type LCD compared with the method for manufacturing the array substrate of the vertical electric field type LCD.
In addition, LCDs can be divided into transmissive, transreflective, and reflective types according to the light for display. Images are displayed by transmitting the light from the backlight in the transmissive LCD, by transmitting the light from the backlight and reflecting the light from the external environment in the transreflective LCD, and by reflecting the light from the external environment in the reflective LCD.
The pixel electrode can be formed of a reflective metal as a reflective plate in the reflective LCD and of a transparent conductive material in the transmissive LCD. In the transreflective LCD, the pixel electrode in the reflective region can be formed of a reflective metal as a reflective plate and the pixel electrode in the transmissive region can be formed of a transparent conductive material.
In order to improve the reflection efficiency of the reflective plate in a reflective LCD or a transreflective LCD, an embossing pattern is formed below the reflective plate so that uneven patterns are formed on the surface of the reflective electrode or the reflective plate.
In addition, many researches have been carried out widely to cut down production cost by reducing the mask number used in producing and improve production efficiency by simplifying the process.
A method of manufacturing an array substrate of a horizontal electric field type liquid crystal display by using a three-mask process has been proposed. Examples of the method can be found in Korean patent applications Nos. 10-2006-0048069 and 10-2006-0011814. The method specifically includes the following steps.
A first patterning process is conducted by subsequently depositing a common electrode layer and a first metal layer on a base substrate, patterning with a first dual tone mask to form a gate line with both the common electrode layer and the first metal layer and an electrode with the common electrode layer in the display region.
A second patterning process is conducted by subsequently depositing a first insulating layer, a semiconductor layer, a doped semiconductor layer, and a second metal layer, patterning with a second dual tone mask to form a TFT channel, a source/drain electrode and a data line.
A third patterning process is conducted by depositing a second insulating layer, patterning with a third dual tone mask to form a via hole in the second insulating layer, ashing the remained photoresist layer to thin the patterned photoresist layer, depositing a pixel electrode layer, and forming an electrode with slits after lifting off the remained photoresist.
Since the common electrode is not required to form on the array substrate of vertical electric field type liquid crystal display, only the gate line is formed in the first patterning process with a full tone mask.
Compared with the method for manufacturing an array substrate of transmissive liquid crystal display, a reflective plate and an embossing pattern below the reflective plate are added when manufacturing an array substrate of transreflective LCD, and thus the mask number used in producing is increased.